Seasonal influenza causes up to 1.5 million deaths worldwide each year. Pandemic influenza killed up to 50 million people during the three pandemics of the last century. Recent spread of avian influenza viruses has raised concerns that another pandemic is looming and could kill millions more. Our ability to deal with a future pandemic is limited in large part by inadequate methods to rapidly vaccinate against new threats. Hypodermic injection of vaccine by medical personnel is extremely time consuming, as seen during the prolonged and inefficient annual influenza vaccination campaigns. To expedite mass vaccination, this project proposes to develop microneedle-based vaccine patches that can be self-administered;do not produce sharp, biohazardous waste;and are low cost. Such patches could be rapidly distributed through pharmacies, fire stations or even the U.S. mail. Because microneedle patches target delivery to skin's dendritic cells, much lower vaccine doses should be needed, which is vital when pandemic vaccine supplies are limited. To accomplish these goals, this project has two Specific Aims. Aim 1 seeks to design and characterize microneedle systems to deliver influenza vaccines to skin. Novel microfabrication techniques will be developed to make microneedles that easily insert into skin to rapidly deliver vaccine to targeted depths. Microneedle designs will be studied using cadaver skin, living human skin explants, and human subjects to determine microneedle mechanical properties;stability during processing and storage;controlled dose targeting and kinetics of vaccine delivery;and safety. These studies will produce microneedles designed to meet the needs of mass immunization against pandemic influenza. Aim 2 seeks to evaluate the efficacy of influenza vaccines delivered using microneedles and determine the role of antigen presenting cells in immune activation. Virus-like particles, purified protein, and DNA vaccines against the H5 influenza strain will be delivered using microneedles to mice and hairless guinea pigs. Microneedle design and vaccination protocol will be optimized based on measuring humoral immune responses, cellular immune responses, memory B cell repertoire, and protection against virus challenge. Cellular pathways to immunity will be evaluated by identifying the role of dendritic and other antigen-presenting cells in immune activation. These aims are strongly integrated, based on Aim 1 microneedle designs motivated by strengths and weaknesses identified in Aim 2 and Aim 2 vaccination studies enabled by the unique microneedle designs from Aim 1. This Bioengineering Research Partnership will be carried out by a collaborative team of five Lead Investigators, including experts in microfabrication, drug delivery, virology, and immunology, with guidance from scientific and industry advisory boards. Future studies anticipate preparation of an IND application to the FDA and initiation of a Phase I clinical trial. Relevance: During an influenza pandemic, microneedle-based vaccination should save lives by rapidly immunizing millions of people using a self-administered, dose-sparing, transdermal patch